Future Power Supply Problem

First off this is a bit like the old is my computer capable of running this thread with a twist. In the future (real soon within the next year) I will upgrading my computer to something simmilar to this.

New nehalem cpu and compatible mobo when they come out
4gigs of ram at least
1 dvd burner
2 new graphic cards in SLI, lets use the 8800 gtx for reference since its power hungry (not planning on that getting that card)
3 750-1 TB HD's
1 veloraptor HD

I was thinking of buying something along the lines of this as the power supply
http://www.newegg.com/Product/Prod [...] 6817703009

And this instead of adding another hard drive cage
http://www.newegg.com/Product/Prod [...] 6817994028

To my understanding power supplies only draw as much power as necessary, and I know that should be able to power everything. The problem is in a couple years I will keep adding more and more hard drives, so im wondering will it still run fine with 9 hard drives in it. Though I probably be using at most 3 hard drives at any given time (the veloraptor as the boot drive, and transfering data between 2 other hard drives)

So I guess the real question is does the other hard drives draw power when they are not in use?
And does everything draw power at full load when I boot up the computer, so will I have a problem with booting up the computer?
Should there be any other problems/concerns I didn't think of?

Actually there is a reason why im avoiding the server idea, I don't usually need access to the other hard drives all that often except for retrieving the odd ball backups that used rarely, as well as tv shows after I get a TV tuner card, and various other stuff. So in general they will be lightly used, I guess I made it sound like I was building a server/gaming machine lol, my bad.

While my goal is a gaming machine with lots of storage and a good enough power supply, not an extreme overkill power supply.

Thats good to know, but will the hard drives still draw that power when not in use?

Most MBs have at most 8 SATA ports, so I'm having difficulty imagining a machine with 10 drives.

Anyway, to answer the question about HDD drawing power when not in use:

http://www.extremetech.com/article [...] 9%2C00.asp

My favorite HDD these days is WD6400AAKS. Here are the numbers for it:
8.3W (average operating); 7.7W idle; 1.00W standby & sleep

Agreed. Here's nVidia's official list of certified PSus for 9800GX2 SLI.
http://www.slizone.com/object/slizone_build_psu.html

The GTX 280 SLI will have exactly the same list, IMO, because GTX 280 and 9800GX2 have almost the same number of stream processors (240, 256 respectively). The list starts at 850W but most are 1000W or higher. Try something like the Corsair 1000HX or the Enermax Galaxy 1000W.

I say at least a PP&C 750 if not doing SLI with a dual GPU card. else, a 1kW PSU.

You got me there, but I know the pack rat gene runs deep in my family so I know it will kick in somehow